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Press statement in response to air change in restaurants


     The Government made the following clarifications today (April 4) in response to recent comments on the air change requirement for catering businesses and the findings of a related site investigation at a restaurant in K11 Musea in early March 2020: 

  • The Centre for Health Protection (CHP) invited Professor KY Yuen, an expert in virology and infectious disease, to join a multidisciplinary team consisting of CHP epidemiologist, the Food and Environmental Hygiene Department, the Electrical and Mechanical Services Department (EMSD), the Environmental Protection Department etc. to conduct a visit to a restaurant in K11 Musea on March 1 to investigate the cause(s) of the cluster of confirmed COVID-19 cases. This was necessary as engineers and epidemiologists do not have expertise in virology and infectious diseases.


  • The air flow measurements taken by the Government during the investigation was about the total outdoor air at the main supply air duct to the seating areas as well as double-checking with the air flow in supply air duct connection to each of the fan coil units where accessible. These sought to simulate the dine-in situations involving the occurrence of this unusual cluster.


  • After the on-site investigation with airflow measurements by engineers, a meeting was chaired by Professor Yuen. All members of this multidisciplinary team listened to all the initial findings reported by different team members, and came up with a consensus of the initial findings and the corresponding recommendations. The conclusion was that the outbreak was more likely due to the low air change per hour (ACH) of 1.2 and 2.1 for certain parts of the dining area of the lower floor on which the outbreak occurred (though two other parts have ACH at 6.1 and 6.4), rather than due to transmission by contact at the adjacent tea room with virus-positive found in the environmental samples, though the latter may have also contributed to the outbreak.


  • There was a comment that air ventilation of the seating area and the kitchen should be taken together for food premises. This is not true. The law requires separate ventilation systems for the seating area and the kitchen and the guide for application for restaurant licences has also made this point clear. The actual ventilation system for the kitchen of the restaurant is in fact connected to the central system of K11 Musea and is completely independent of that for its seating area.


  • We also wish to clarify that no Government departments, including the EMSD, have been commissioned to do any study referred to by the restaurant on March 31.


  • While Professor Yuen did suggest the need of at least six ACH in eateries or putting in place air purifiers meeting certain specifications as an alternative, as short-range air-borne transmission of COVID-19 is now known to be important in indoor settings with poor ventilation and mask off activities, the Government did conduct literature review in August/September 2020 and take a view on adopting this threshold as the basis for the voluntary declaration system launched on October 16, 2020, which was now codified into the mandatory registration system.  


  • In summary, the experts involved in the K11 Musea investigation have considered all available evidence thoroughly and exercised their duty and judgement based on scientific evidence and professional knowledge. Current available information does not indicate any flaws in the investigation process. The requirements of ACH in eateries or air purifiers as an alternative are based on scientific evidence available, overseas guidelines and consensus of experts of relevant disciplines.